The present invention relates to drop-outs for attaching bicycle axles to a bicycle frame, and to the manner of attachment of the drop-outs within receiving tubes of the frame.
The front and rear axles of a typical bicycle are attached to the front fork and frame, respectively, of the bicycle. In particular, the axles are retained in slotted elements called "drop-outs" which are welded to receiving tube portions of the front fork and frame, respectively. Depicted in FIG. 8 is a rear axle drop-out 1 which includes a slot 2 for receiving a bicycle rear axle. The drop-out 1 also includes a pair of legs 3, 4 secured in receiving tubes 5, 6 formed as part of a bicycle frame. In FIG. 9 there is depicted a front axle drop-out 7 which includes a slot 8 for receiving a bicycle front axle, and a leg 9 securable in a receiving tube 10 formed as part of a front fork of the bicycle.
Different techniques have been heretofore practiced for securing the legs of the drop-outs to their respective receiving tubes. For example, in a so-called slotted tube method depicted in FIG. 10 the receiving tube 10 is provided with a central slot 12 which receives a rear end 14 of the leg 9 of the drop-out 7. The end of the receiving tube is domed inwardly against the drop-out leg to close the tube. The tube and drop-out leg are welded together. Among other disadvantages, this slotted tube technique involves the need to perform considerable preparation work on the tube end to create the drop-out receiving slot 12 and to form the dome 16. Also, it is difficult to vary the position of the drop-out relative to the end of the tube.
A variation of the slotted tube method, called the cover plate method, involves locating the drop-out leg to one side of the tube rather than being centered therein. A cover plate is positioned over the opening between the opposite side of the tube and the drop-out leg. The cover plate and drop-out leg are welded to the tube and to each other. This technique requires less preparation of the tube than the slotted tube method, but involves more fit-up and welding time due to the need to install the separate cover plate.
Yet another drop-out securing technique, called the plug method is depicted in FIG. 11. That technique involves inserting a plug 18 into the receiving tube 5 and then welding it to the tube such that the plug projects beyond the end of the tube. The drop-out is then welded to the exposed end of the plug. Shortcomings of this technique are similar to those encountered above, i.e., a substantial fit-up and welding time.
It would, therefore, be desirable to enable a drop-out to be welded to a receiving tube of a bicycle frame or front fork with minimal time and effort.